The invention relates to a method of filtering cellulose acetate solutions as well as to a plant for carrying out the method.
When producing acetate rayon (artificial silk), it is necessary to carefully filter the highly viscous cellulose acetate solution so as to obtain favorable fiber properties. It has been known to carry out the filtration by means of filter presses (Ullmanns Encyklopadie der technischen Chemie, 3rd Editlion, Vol. 3, pp.17 to 20). Such filter presses must be supplied with various filtering aids--such as, e.g., filter cloths of cellulose or fabric, or other precoating means.
In a continuous production process, these filter presses will be clogged after a few days at the latest, and the filtering aids or precoating means will have to be disposed of.
Filter presses are regenerated by being opened and supplied with new filtering aids. This results in a substantial loss of cellulose acetate, which may be reduced by washing the filters with solvent. All of these manipulations must be carried out in a "solvent atmosphere". Since acetone is used as the solvent, the wearing of gas masks becomes indispensible, and there is a constant danger of explosion.